The invention relates to devices which grip tubular members, such as a drill pipe. More particularly, the invention relates to locking collars for positioning and affixing objects to a drill pipe.
In the field of oil well drilling, various tools and appliances, such as centralizers, scratchers, solidifiers, baskets, and the like, have been developed for centering the casing within the wellbore or for cleaning or otherwise scraping the walls of the bore to facilitate the placing of the cement column around the casing and to assure a satisfactory bonding of the column to the wall of the well. In addition, various tools and sensors must be located downhole in a wellbore which are typically mounted upon the well casing.
Well drilling is a time consuming and expensive operation. Costs and manpower require that every operation be completed as quickly and efficiently as possible. Thus, downhole tools and sensors must be positioned and locked upon a pipe casing as quickly as possible.
“Locking collars”, also known as “stop collars”, have been used for centuries to hold objects and prevent them from sliding longitudinally upon an elongate object such as a pipe or rod. A wide variety of fasteners have been employed to affix stop collars upon the casing, ranging from welding, or friction fits using bolts, setscrews, or wedging pin arrangements. Additional structures to prevent the stop collar from moving longitudinally upon the casing including the use of knockdown buckles or low friction surfaces such as teeth.
Fasteners are often time consuming to install, and require torque measurement or other methods to assure adequate resistance to longitudinal sliding. For example, each buckle of a knockdown buckle must be hammered against the well casing for proper engagement. Further, aside from welding which is cost and time prohibitive, all fastener constructions risk longitudinal sliding due to vibration or other forces. If forced to slide, setscrews, bolts and wedges can score the casing reducing its integrity which can cause failure burst, leaking or deformation.
Previous stop collars have a perpendicular leading edge so that longitudinal force creates an even sliding force on the stop collar. This sliding force can overcome the friction from set screws, wedges or other tightening means causing stop collars to slide. Further, this sliding can cause set screws or wedges to score or damage a pipe or shaft, thus reducing its integrity. Pipe integrity is critical in many installations such as oil pipelines, hydraulics and other high-performance applications.
Therefore, there remains a need for a stop collar that allows for the positioning of downhole tools, sensors and other objects that may be installed quickly and easily.
There is also a need for a stop collar that is not subject to disengagement due to vibration and other similar forces.
Furthermore, there is a need for a stop collar with a minimum of components to facilitate installation and decrease the probability of failure.